Electroosmotic Flow in Hydrophobic Microchannels of General Cross Section

2015 ◽  
Vol 138 (3) ◽  
Author(s):  
Morteza Sadeghi ◽  
Arman Sadeghi ◽  
Mohammad Hassan Saidi
Keyword(s):  
Cross Section ◽  
Flow Rate ◽  
Electroosmotic Flow ◽  
Slip Length ◽  
Debye Length ◽  
Surface Hydrophobicity ◽  
Double Layers ◽  
Slip Conditions ◽  
Wall Boundary Conditions ◽  
Electroosmotic Velocity

Adopting the Navier slip conditions, we analyze the fully developed electroosmotic flow in hydrophobic microducts of general cross section under the Debye–Hückel approximation. The method of analysis includes series solutions which their coefficients are obtained by applying the wall boundary conditions using the least-squares matching method. Although the procedure is general enough to be applied to almost any arbitrary cross section, eight microgeometries including trapezoidal, double-trapezoidal, isosceles triangular, rhombic, elliptical, semi-elliptical, rectangular, and isotropically etched profiles are selected for presentation. We find that the flow rate is a linear increasing function of the slip length with thinner electric double layers (EDLs) providing higher slip effects. We also discover that, unlike the no-slip conditions, there is not a limit for the electroosmotic velocity when EDL extent is reduced. In fact, utilizing an analysis valid for very thin EDLs, it is shown that the maximum electroosmotic velocity in the presence of surface hydrophobicity is by a factor of slip length to Debye length higher than the Helmholtz–Smoluchowski velocity. This approximate procedure also provides an expression for the flow rate which is almost exact when the ratio of the channel hydraulic diameter to the Debye length is equal to or higher than 50.

scholarly journals Electroosmotic Flow of Viscoelastic Fluid in a Nanochannel Connecting Two Reservoirs

Micromachines ◽  
2019 ◽  
Vol 10 (11) ◽  
pp. 747 ◽  
Author(s):  
Mei ◽  
Qian
Keyword(s):  
Constitutive Model ◽  
Viscoelastic Fluid ◽  
Flow Rate ◽  
Electroosmotic Flow ◽  
Double Layers ◽  
Ionic Conductance ◽  
Electrical Double Layers ◽  
Interconnect System ◽  
First Time ◽  
Thinning Effect

: Electroosmotic flow (EOF) of viscoelastic fluid with Linear Phan-Thien–Tanner (LPTT) constitutive model in a nanochannel connecting two reservoirs is numerically studied. For the first time, the influence of viscoelasticity on the EOF and the ionic conductance in the micro-nanofluidic interconnect system, with consideration of the electrical double layers (EDLs), is investigated. Regardless of the bulk salt concentration, significant enhancement of the flow rate is observed for viscoelastic fluid compared to the Newtonian fluid, due to the shear thinning effect. An increase in the ionic conductance of the nanochannel occurs for the viscoelastic fluid. The enhancement of the ionic conductance is significant under the overlapping EDLs condition.

Slippage Effect on the Oscillatory Electroosmotic Flow of Power-Law Fluids in a Microchannel

2020 ◽  
Vol 399 ◽  
pp. 92-101
Author(s):  
Ruben Baños ◽  
José Arcos ◽  
Oscar Bautista ◽  
Federico Méndez
Keyword(s):  
Power Law ◽  
Electroosmotic Flow ◽  
Characteristic Length ◽  
Slip Length ◽  
Flow Behavior ◽  
Debye Length ◽  
Channel Width ◽  
Length Scale ◽  
Characteristic Length Scale ◽  
Power Law Fluids

The oscillatory electroosmotic flow (OEOF) under the influence of the Navier slip condition in power law fluids through a microchannel is studied numerically. A time-dependent external electric field (AC) is suddenly imposed at the ends of the microchannel which induces the fluid motion. The continuity and momentum equations in the and direction for the flow field were simplified in the limit of the lubrication approximation theory (LAT), and then solved using a numerical scheme. The solution of the electric potential is based on the Debye-Hückel approximation which suggest that the surface potential is small, say, smaller than 0:025V and for a symmetric () electrolyte. Our results suggest that the velocity profiles across the channel-width are controlled by the following dimensionless parameters: the dimensionless slip length , the Womersley number, , the electrokinetic parameter, , defined as the ratio of the characteristic length scale to the Debye length, the parameter which represents the ratio of the Helmholtz-Smoluchowski velocity to the characteristic length scale and the flow behavior index, . Also, the results reveal that the velocity magnitude gets higher values as increases and become more and more nonuniform across the channel-width as the and are increased, so OEOF can be useful in micro-fluidic devices such as micro-mixers.

scholarly journals Steric and Slippage Effects on Mass Transport by Using an Oscillatory Electroosmotic Flow of Power-Law Fluids

Micromachines ◽  
2021 ◽  
Vol 12 (5) ◽  
pp. 539
Author(s):  
Ruben Baños ◽  
José Arcos ◽  
Oscar Bautista ◽  
Federico Méndez
Keyword(s):  
Mass Transport ◽  
Electroosmotic Flow ◽  
Volume Fraction ◽  
Slip Length ◽  
Electrical Potential ◽  
Debye Length ◽  
Ion Concentration ◽  
Steric Effects ◽  
Power Law Fluids ◽  
Poisson Boltzmann

In this paper, the combined effect of the fluid rheology, finite-sized ions, and slippage toward augmenting a non-reacting solute’s mass transport due to an oscillatory electroosmotic flow (OEOF) is determined. Bikerman’s model is used to include the finite-sized ions (steric effects) in the original Poisson-Boltzmann (PB) equation. The volume fraction of ions quantifies the steric effects in the modified Poisson-Boltzmann (MPB) equation to predict the electrical potential and the ion concentration close to the charged microchannel walls. The hydrodynamics is affected by slippage, in which the slip length was used as an index for wall hydrophobicity. A conventional finite difference scheme was used to solve the momentum and species transport equations in the lubrication limit together with the MPB equation. The results suggest that the combined slippage and steric effects promote the best conditions to enhance the mass transport of species in about 90% compared with no steric effect with proper choices of the Debye length, Navier length, steric factor, Womersley number, and the tidal displacement.

Computational and theoretical research of the injector block function

2020 ◽  
pp. 123-126
Author(s):  
В.В. Кожемякин ◽  
Р.А. Иванов ◽  
Е.С. Игнатьева
Keyword(s):  
Hydraulic Resistance ◽  
Cross Section ◽  
Flow Rate ◽  
Pressure Dependence ◽  
Theoretical Study ◽  
Water Jet ◽  
Theoretical Research ◽  
Sudden Expansion ◽  
Operating Modes ◽  
Coefficient Of Hydraulic Resistance

Работа посвящена расчетно-теоретическому исследованию работы блока инжекторов. Рассмотрен пароводяной струйный аппарат, который применяется в качестве средства циркуляции теплоносителя первого контура. Подвод дополнительного потока осуществляется на цилиндрическом участке с внезапным расширением сечения через перемычку. Для достижения поставленной цели разработана программа для ЭМВ, в которой смоделирована зависимость давления от нагрузки в контуре, а также проведено расчетно-теоретическое исследование влияние гидравлического сопротивления на расход перемычки. В данной работе рассмотрены только рабочие режимы, т.е. все инжекторы работают как насосы. В ходе работы было установлено, что при нагрузке в 30% увеличиваются коэффициенты инжекции пароводяного струйного аппарата, но характер работы перемычек не меняется. Так же было установлено, что расход через перемычку меняется не пропорционально коэффициенту гидравлического сопротивления перемычки. The paper is devoted to the computational and theoretical study of the injector block operation. A steam-water jet apparatus is considered, which is used as a means of circulating the primary circle coolant. The additional flow is supplied on the cylindrical section with a sudden expansion of the cross-section through the bridge. To achieve this goal, a computer program was developed that modeled the pressure dependence on the load in the circuit, and also a theoretical study of the influence of hydraulic resistance on the flow of the jumper was conducted. In this paper, only operating modes are considered, i.e. all the injectors function as pumps. In the process of the research, it was found that at a load of 30%, the injection coefficients of the steam-water jet apparatus increase, but the nature of the work of the jumpers does not change. It was also found out that the flow rate through the jumper does not change in proportion to the coefficient of hydraulic resistance of the jumper.

On the Influence of the Slot Orifice in Diesel Common Rail Nozzle

2018 ◽  
Vol 11 (1) ◽  
pp. 55-69 ◽  
Author(s):  
Giancarlo Chiatti ◽  
Ornella Chiavola ◽  
Fulvio Palmieri ◽  
Roberto Pompei
Keyword(s):  
Cross Section ◽  
Flow Rate ◽  
Experimental Analysis ◽  
Common Rail ◽  
Spray Angle ◽  
The Novel ◽  
Hydraulic Behavior ◽  
Reference Information ◽  
Light Duty ◽  
Set Up

Background:The paper deals with a diesel common rail nozzle in which a novel orifice layout is implemented.Objective:Its influence on the nozzle mechanical-hydraulic behavior and on the spray shape transient development is experimentally investigated.Methods:In the research, a solenoid injector for light duty diesel engines is equipped with the novel nozzle prototype and tested. The prototype layout is described, pointing out the features of the nozzle orifices, in which a Slot cross-section is adopted; the investigation is accomplished extending the hydraulic tests and the spray visualizations to a reference nozzle with standard holes. The influence of the hole layout on the mechanical-hydraulic behavior of the nozzle is assessed by experimental analysis based on the rate of injection measurement, in comparison with the reference nozzle. Once the hydraulic behavior of the novel nozzle has been characterized in terms of mass flow rate, the slot influence on the spray shape is assessed analyzing the macroscopic features such as the penetration distance and the spray angle, in non evaporative conditions. The study is carried out under transient injection conditions, for different injection pressures, up to 1400 bar.Results:The results on spray characteristics also provide reference information to set up spray models suited to take the Slot orifice into account.

Electrokinetics of polymeric fluids in narrow rectangular confinements

Soft Matter ◽  
2021 ◽  
Author(s):  
Aditya Natu ◽  
Uddipta Ghosh
Keyword(s):  
Cross Section ◽  
Rectangular Cross Section ◽  
Double Layers ◽  
Polymeric Fluids ◽  
Polymeric Liquids ◽  
Electrical Double Layers

Flow of polymeric liquids in narrow confinements of rectangular cross section, in the presence of electrical double layers is analyzed here. Our analysis is motivated by the fact that many...

The Design and Simulation for a Novel Electroosmotic Micromixer

2006 ◽  
Author(s):  
Hongjun Song ◽  
Xie-Zhen Yin ◽  
Dawn J. Bennett
Keyword(s):  
Electric Field ◽  
Cross Section ◽  
Chemical Reactions ◽  
Electroosmotic Flow ◽  
Chaotic Advection ◽  
Microfluidic Systems ◽  
Mixing Effect ◽  
Passive Mixers ◽  
The Cross ◽  
External Forces

The analysis of fluid mixing in microfluidic systems is useful for many biological and chemical applications at the micro scale such as the separation of biological cells, chemical reactions, and drug delivery. The mixing of fluids is a very important factor in chemical reactions and often determines the reaction velocity. However, the mixing of fluids in microfluidics tends to be very slow, and thus the need to improve the mixing effect is a critical challenge for the development of the microfluidic systems. Micromixers can be classified into two types, active micromixers and passive micromixers. Passive micromixers depend on changing the structure and shape of microchannels in order to generate chaotic advection and to increase the mixing area. Thus, the mixing effect is enhanced without any help from external forces. Although passive micromixers have the advantage of being easily fabricated and requiring no external energy, there are also some disadvantages. For example, passive mixers often lack flexibility and power. Passive mixers rely on the geometrical properties of the channel shapes to induce complicated fluid particle trajectories thereby enhancing the mixing effect. On the other hand, active micromixers induce a time-dependent perturbation in the fluid flow. Active micromixers mainly use external forces for mixing including ultrasonic vibration, dielectrophoresis, magnetic force, electrohydrodynamic, and electroosmosis force. However, the complexity of their fabrication limits the application of active micromixers. In this paper we present a novel electroosmotic micromixer using the electroosmotic flow in the cross section to enhance the mixing effect. A DC electric field is applied to a pair of electrodes which are placed at the bottom of the channel. A transverse flow is generated in the cross section due to electroosmotic flow. Numerical simulations are investigated using a commercial software Fluent® which demonstrates how the device enhances the mixing effect. The mixing effect is increased when the magnitude of the electric field increased. The influences of Pe´clet number are also discussed. Finally, a simple fabrication using polymeric materials such as SU-8 and PDMS is presented.

Evaporation and Viscous Flow in Triangular Grooves in Micro Heat Pipes

2005 ◽  
Author(s):  
Mulugeta Markos ◽  
Vladimir S. Ajaev ◽  
G. M. Homsy
Keyword(s):  
Cross Section ◽  
Flow Rate ◽  
Cross Sections ◽  
Wedge Angle ◽  
Heat Pipes ◽  
Type Model ◽  
Pressure Gradients ◽  
Maximum Value ◽  
Dry Out ◽  
Micro Heat Pipes

We develop a lubrication type model of a liquid flow in a wedge in the limit of small capillary numbers and negligible gravity. The model incorporates the effects of capillary pressure gradients and evaporation. Steady vapor-liquid interface shapes are found for a range of parameters. In the limit of weak evaporation the flow is the same in all cross-sections and can be controlled by changing the wedge angle. We find the wedge angle that results in the maximum value of the flow rate for a given contact angle. For high evaporation rates, both the flow rate and the amount of liquid in each cross-section along the wedge decrease until the point of dry-out is reached. The location of the dry-out point is studied as a function of evaporation. Practical suggestions about optimization of micro heat pipes are given.

A new method for prediction of the acoustic performance and design parameter sensitivity analysis of multi-chamber perforated resonators with an irregular cross-section

2021 ◽  
pp. 1-24
Author(s):  
Rong Guo ◽  
Zanzan Sun ◽  
Zhen Huang ◽  
Rui Luo
Keyword(s):  
Theoretical Prediction ◽  
Cross Section ◽  
Flow Rate ◽  
New Method ◽  
Frequency Noise ◽  
Acoustic Characteristics ◽  
Inlet Flow ◽  
Acoustic Performance ◽  
Inlet Flow Rate ◽  
Prediction Approach

Abstract Aiming at reducing the high-amplitude and wide-frequency noise in charged air intake system of the powertrain, this paper proposes a new method for predicting the acoustic characteristics of an irregular cross-section multi-chamber perforated resonator under flow conditions. By this method, the presence of three-dimensional sound waves and the effects of higher-order modes are considered, and the acoustic performance of the resonator can be evaluated through the computation of transmission loss. Moreover, by discretizing the cross-section of perforated resonator and extracting node information, this method can solve the acoustic characteristics of the perforated resonator with any cross-section. Based on the transfer matrix method, the quadrupole parameters of each chamber are obtained. Then the acoustic characteristics of the multi-chamber perforated resonator could be calculated. The theoretical prediction data and the experimental data have been compared and the results show good agreement within the entire frequency range, which verifies the accuracy of the theoretical prediction approach. Based on this prediction approach, the influence of section ratio, structure parameters and inlet flow rate on the acoustic characteristics of the resonator is explored. The results show that when the structural parameters change, the peak resonance frequency of the resonator will have a regular shift. With the increase of the inlet flow rate, the main frequency band of sound attenuation will decrease significantly. The theoretical method developed in this work can be used for the calculation and optimization of multi-chamber resonators in various applications.

Electroosmotic flow of Maxwell fluid in a microchannel of isosceles right triangular cross section

2021 ◽  
Vol 33 (12) ◽  
pp. 123113
Author(s):  
Xu Yang ◽  
Shaowei Wang ◽  
Moli Zhao ◽  
Yue Xiao
Keyword(s):  
Cross Section ◽  
Electroosmotic Flow ◽  
Maxwell Fluid ◽  
Triangular Cross Section
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